Re: dns and software, was Re: Reliable Cloud host ?

[Mark Andrews <marka () isc org>]

In message <596196444196086313@unknownmsgid>, Matt Addison writes:
> On Mar 1, 2012, at 17:10, William Herrin <bill () herrin us> wrote:
> > If took you 50 lines of code to do
> > 'socket=connect("www.google.com",80,TCP);' and you still managed to
> > produce a version which, due to the timeout on dead addresses, is
> > worthless for any kind of interactive program like a web browser. And
> > because that code isn't found in a system library, every single
> > application programmer has to write it all over again.
> >
> > I'm a fan of Rube Goldberg machines but that was ridiculous.
>
> I'm thinking for this to work it would have to be 2 separate calls:
>
> Call 1 being to the resolver (using lwres, system resolver, or
> whatever you want to use) and returning an array of struct addrinfo-
> same as gai does currently. If applications need TTL/SRV/$NEWRR
> awareness it would be implemented here.
>
> Call 2 would be a "happy eyeballs" connect syscall (mconnect? In the
> spirit of sendmmsg) which accepts an array of struct addrinfo and
> returns an fd. In the case of O_NONBLOCK it would return a dummy fd
> (as non-blocking connects do currently) then once one of the
> connections finishes handshake the kernel connects it to the FD and
> signals writable to trigger select/poll/epoll. This allows developers
> to keep using the same loops (and most of the APIs) they're already
> comfortable with, keeps DNS out of the kernel, but hopefully provides
> a better and easier to use connect() experience, for SOCK_STREAM at
> least.
>
> It's not as neat as a single connect() accepting a name, but seems to
> be a happy medium and provides a standardized/predictable connect()
> experience without breaking existing APIs.
>
> ~Matt

And you can do the same in userland with kqueue and similar.

int
connectxx(struct addrinfo *res0, int *fd, int *timeout, void**state);

0 *fd is a connected socket.
EINPROGRESS Wait on '*fd' with a timeout of 'timeout' nanoseconds.
ETIMEDOUT connect failed.

If timeout or state is NULL you block.
You re-call with res0 set to NULL.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka () isc org